Mary, the all-holy ever-virgin Mother of God, is the masterwork of the mission of the Son and the Spirit in the fullness of time. For the first time in the plan of salvation and because his Spirit had prepared her, the Father found the dwelling place where his Son and his Spirit could dwell among men. In this sense the Church’s Tradition has often read the most beautiful texts on wisdom in relation to Mary. Mary is acclaimed and represented in the liturgy as the “Seat of Wisdom.”
In her, the “wonders of God” that the Spirit was to fulfill in Christ and the Church began to be manifested:
The Holy Spirit prepared Mary by his grace. It was fitting that the mother of him in whom “the whole fullness of deity dwells bodily” should herself be “full of grace.” She was, by sheer grace, conceived without sin as the most humble of creatures, the most capable of welcoming the inexpressible gift of the Almighty. It was quite correct for the angel Gabriel to greet her as the “Daughter of Zion”: “Rejoice.” It is the thanksgiving of the whole People of God, and thus of the Church, which Mary in her canticle lifts up to the Father in the Holy Spirit while carrying within her the eternal Son.
In Mary, the Holy Spirit fulfills the plan of the Father’s loving goodness. With and through the Holy Spirit, the Virgin conceives and gives birth to the Son of God. By the Holy Spirit’s power and her faith, her virginity became uniquely fruitful.
In Mary, the Holy Spirit manifests the Son of the Father, now become the Son of the Virgin. She is the burning bush of the definitive theophany. Filled with the Holy Spirit she makes the Word visible in the humility of his flesh. It is to the poor and the first representatives of the gentiles that she makes him known.
Finally, through Mary, the Holy Spirit begins to bring men, the objects of God’s merciful love, into communion with Christ. and the humble are always the first to accept him: shepherds, magi, Simeon and Anna, the bride and groom at Cana, and the first disciples.
At the end of this mission of the Spirit, Mary became the Woman, the new Eve (“mother of the living”), the mother of the “whole Christ.” As such, she was present with the Twelve, who “with one accord devoted themselves to prayer,” at the dawn of the “end time” which the Spirit was to inaugurate on the morning of Pentecost with the manifestation of the Church.
From the Catechism of the Catholic Church 721-726